disappearance and return of harbor porpoise to puget...

STATE OF WASHINGTON JANUARY 2016

DISAPPEARANCE AND RETURN OF HARBOR PORPOISE TO PUGET SOUND:

20 YEAR PATTERN REVEALED FROM WINTER AERIAL SURVEYS

Evenson, J.R., D. Anderson, B.L. Murphie, T.A. Cyra, and J. Calambokidis

Technical Report

Disappearance and Return of Harbor Porpoise to Puget Sound: 20 Year Pattern Revealed from Winter Aerial Surveys

Evenson, J.R., D. Anderson, B.L. Murphie, T.A. Cyra, and J. Calambokidis. 2016 1 | P a g e

Recommended Citation: Evenson, J.R., D. Anderson, B.L. Murphie, T.A. Cyra, and J.

Calambokidis. 2016. Disappearance and return of harbor porpoise to Puget Sound: 20 year

pattern revealed from winter aerial surveys. Technical Report. Washington Department of Fish

and Wildlife, Wildlife Program and Cascadia Research Collective, Olympia, WA.

Cover Image: Puget Sound Harbor Porpoise (Joseph Evenson, WDFW) with DHC-2 Beaver inset

(Tom Cyra, WDFW).



RETURN OF HARBOR PORPOISE TO PUGET SOUND:

20 YEAR PATTERN REVEALED FROM WINTER AERIAL SURVEYS

Evenson, J.R.1, D. Anderson2, B.L. Murphie1, T.A. Cyra1, and J. Calambokidis2

1Washington Department of Fish and Wildlife,

Wildlife Program,

600 Capitol Way North Olympia, WA 98501-1091

2Cascadia Research Collective,

218 1/2 W 4th Ave., Olympia, WA 98501

January 2016



Summary Harbor porpoise were a common year-round resident in the Puget Sound in the 1940s, but by

the 1970s, they had disappeared from the Sound, and their numbers were greatly reduced in

the Straits of Georgia and Juan de Fuca, and around the San Juan Islands. Some survey efforts

were conducted to verify that there were no harbor porpoise within the Puget Sound, but prior

to 2013, there were no dedicated small cetacean surveys providing complete coverage of

Washington’s inland waters, including the Puget Sound. Beginning in the early 2000s, there

were increasing reports of harbor porpoise sightings by the public, and by researchers involved

in other activities on the water. Unfortunately, there wasn’t funding during this period for the

National Marine Fisheries Service (NMFS) to conduct aerial surveys of the inland Washington

harbor porpoise stock, leaving many questions about the increase in sighting reports

unanswered.

Washington Department of Fish & Wildlife (WDFW) conducts annual winter aerial marine bird

surveys that cover all of the Washington inner marine waters from southern Puget Sound to the

Canadian border, out to the west entrance of the Strait of Juan de Fuca. These surveys have

been conducted every year (except 2007) since 1994, and record all marine mammal

observations in addition to the marine bird observations. While it is not designed as a

dedicated marine mammal survey, because of the consistent survey methodology throughout

the survey area, and that all marine mammal observations were recorded, this 20-year dataset

provides a record of increasing harbor porpoise numbers in the northern portion of the survey

area in the early years, followed by their expansion into the waters of the Puget Sound. The

rate of increase exceeds the maximum potential local recruitment rate, not only within the

Puget Sound, but throughout the inland marine waters, suggesting immigration from outside

the study area is supplementing recruitment.

During this same period, reports of Dall’s porpoise had been decreasing, concurrent to the

increase in harbor porpoise sightings. These surveys confirmed a downward trend in Dall’s

porpoise numbers, with none sighted in 2014.



Acknowledgements We would foremost like to thank Dave Nysewander for his efforts in establishing the survey and

in seeing that the surveys continued while he was the project leader; it is thanks to Dave’s

leadership that this survey exists as it is today with the high regard it enjoys. We are grateful to

Don Kraege for his continued support for the survey since its inception, and for his efforts in

seeing that the survey maintained funding during the various cycles of budget cuts; it is because

of the primary objective of the survey to monitor winter sea duck population trends to set

hunting regulations, and the funding from the Pittman–Robertson Federal Aid in Wildlife

Restoration Act to meet these objectives, that these surveys are even possible. We are also

very grateful to Don for his constant support in the safety of the crew by supporting all of the

trainings identified and requested, as well as the acquisition of all safety equipment identified

to ensure the safety of the flight crew. We are greatly indebted to the many pilots who have

flown these survey over the years. The primary pilots were Val Judkins and Jim Hodgson with

WDFW, Mark Schoening with Sound Flight, and Chuck Perry with Kenmore Air. We are

especially thankful to Kenmore Air and Chuck Perry for their enthusiasm, professionalism, focus

on flight safety, and continued support in working with us as the survey has evolved to follow

the current standardized transect lines; we are also grateful to the Kenmore mechanics for their

superb detail regarding the maintenance of the survey aircraft. We thank Matt Nixon, Wendy

Parsons, and Warren Michaellis for serving as observers during the early years of the survey.

Finally, we are indebted to the many flight followers who have tracked our flights over the

years, these include Kye Iris, Don Kraege, Ruth Milner, Debbie Moe, Mikal Moore, Dave

Nysewander, Scott Pearson, Carol Powers, Celia Roberts, Jeff Skriletz, and Heather

Tschaekofske; we apologize for those we may have left off this list.

Primary survey flight crew and aircraft (from left to right) B. Murphie, T. Cyra, J. Evenson, and C. Perry, in front of N900KA “Maggie”, the last Beaver commercially manufactured by de Havilland.



Introduction Harbor porpoise (Phocoena phocoena) were considered the most common cetacean in the

inner marine waters of Washington State including Puget Sound in the 1940s, the most

common cetacean in Washington state-wide, and seen year round in the Puget Sound (Scheffer

& Slipp 1948). Research and observations from the 1970s through the 1990s, however,

revealed harbor porpoise were virtually absent from PS (Everitt et al. 1980; Osborne et al. 1988;

Osmek et al. 1996; Laake et al. 1997; Calambokidis & Baird 1994) so systematic aerial surveys to

estimate abundance generally did not even include these waters. Reports of harbor porpoise

within the Puget Sound began in the early 2000s, with regular sightings in southern Puget

Sound starting in 2008. The return was monitored by NMFS, WDFW, Cascadia Research

Collective (CRC) and the Marine Mammal Stranding Network. This included several stranded

animals within the Puget Sound during the Unusual Mortality Event (UME) of 2006-2007

(Huggins et al. 2015).

Eastern Pacific harbor porpoise are distributed almost continuously along the west coast of the

United States and Canada. They are considered non-migratory and relatively resident to

specific areas with NMFS recognizing six different management stocks along the US West Coast

based on genetic and contaminant research (Calambokidis & Barlow 1991; Chivers et al. 2002;

Chivers et al. 2007; Sveegaard et al. 2012; Carretta et al. 2012).

Dall’s porpoise (Phocoenoides dalli) also occur in Puget Sound but are considered to be a more

pelagic species (Carretta et al. 2012). Though Scheffer and Slipp (1948) mention Dall’s

porpoise, it is unclear whether any of the sightings were in the inner marine waters, or if the

animals were caught off the coastal waters by boats that returned to inland ports. Other

records from the middle of the 20th century included sightings in inland waters in British

Columbia during the summer and fall, but only in the wide straits and channels with fast

currents, with no Dall’s porpoise sighted in any of the narrow passages or bays frequented by

harbor porpoise (Scheffer 1949; Cowan 1944). Cowen (1944) specifically noted that Dall’s

porpoise had not been recorded in the Strait of Juan de Fuca or the Gulf of Georgia (includes all

marine waters east of SJF). Reports during the 1960s, 1970s and 1980s documented Dall’s

porpoise presence in the inland waters during all months of the year, with the center of

abundance in the Strait of Juan de Fuca, including animals sighted as far east as Rosario Strait,

and down into the central Puget Sound Basin, with occasional sightings into the south Puget

Sound. Dall’s porpoise were not reported in the Strait of Georgia, Whidbey Basin or the Hood

Canal (Everitt et al. 1980; Pike & MacAskie 1969; Miller 1990). Abundance in inland waters

appears to be seasonally dependent in other inland areas of the Dall’s porpoise range, with

greater numbers appearing in the summer than during other times of the year (Cowan 1944),

and this is supported by the few studies published for the Strait of Juan de Fuca and the Puget

Sound (Miller 1990). A photo-ID study conducted in the Central Puget Sound and Admiralty

Inlet in 1987-1988 had few resightings, which combined with their changing seasonal



abundance, suggest that their presence in the inland waters could be transitory in nature

(Miller 1990).

The Washington Department of Fish and Wildlife has conducted winter aerial marine surveys

since 1993. Beginning in 1995 all marine mammal sightings were recorded. While not designed

to study marine mammals, these surveys provide the most comprehensive documentation of

the changes in porpoise populations in Washington’s inner marine waters.

A variety of factors undoubtedly lead to the near extirpation of harbor porpoise from the Puget

Sound. It is beyond the scope of this paper to fully explore, yet the inner marine waters were

subject to most of the commonly cited threats to harbor porpoise populations. Interactions

with fisheries and pollution are two threats that were a known problem in the inner marine

waters during the period of harbor porpoise decline. Changes have been made in recent

decades that would reduce the impact of these threats, allowing the Washington Inland Waters

Stock of harbor porpoise to increase to its current level.

Fisheries interactions, specifically gillnet and set-net fishing is commonly considered to be the

greatest threat to most porpoise populations (Hammond et al. 2008), and likely were the major

factor in the unsustainable reduction in the Washington inland harbor porpoise stock. Scheffer

& Slipp (1948) mention many bycaught porpoise in many of the fisheries, including gillnets,

deep nets for shark fisheries, fish traps, trawls and seines. Fisheries records show a dramatic

increase in the number of commercial licenses issued in the post-WWII years. Commercial and

tribal salmon fisheries are now managed to recover endangered salmonid runs, with a smaller

fleet, few fishing days, exclusion zones and bycatch reduction efforts required (Washington

Department of Fish and Wildlife 2015). Pressures on harbor porpoise from other net based

fisheries are also greatly reduced, as dogfish and cod bottom set nets, most trawl fishing, are no

longer legal within PS (WAC 220-48-015).

Pollution can have both a direct impact on harbor porpoise, as well as leading to a reduction in

prey. Harbor porpoise are high trophic level predators, with bioaccumulation of pollutants a

concern (Bossart 2011); pollutants including heavy metals, organochlorides and PAHs have

been implicated in weakened immune systems and reduced reproductive success (Bennett et

al. 2001; Law et al. 1991; Law et al. 2002). Pollution has been, and continues to be a major

problem within inshore marine waters (Dexter et al. 1985; Ecology & King County 2011).

Studies of harbor seals have shown levels of many pollutants, including DDE and PCB, were

concentrated at much higher levels in tissues of animals in the southern Puget Sound compared

to the animals in the eastern Strait of Juan de Fuca and San Juan Islands (Calambokidis et al.

1984). Many sources of pollution have been eliminated or cleaned up in recent decades,

including the elimination of a smelter near Tacoma, and several pulp mills, and tighter

regulation of remaining point source polluters.

Several other factors have been suggested for the decline of harbor porpoise in the inside

marine waters, including higher levels of vessel traffic, increasing noise pollution remain, which



suggests that they are not the underlying factors of the decline, or to have hindered the

recovery of the stock.

Methods

Study Area The study was conducted in the inner marine waters of Washington State (Figure 1). These

include the Strait of Juan de Fuca (SJF), the Puget Sound (PS) and Washington Sound/San Juan

Archipelago to the Canadian border (WS) (Figure 1). The study area was divided into nine

basins separated by prominent sills or other geographic features. These basins are commonly

used to delineate both hydrographically and biologically distinct areas within the inland waters

throughout a variety of studies. The Western Strait of Juan de Fuca (WSJF) basin runs from the

Pacific Ocean to Ediz Hook, near Port Angeles, with the Eastern Strait of Juan de Fuca (ESJF)

Figure 1. The inner marine waters of Washington State include 9 basins generally separated by sills; these were grouped into three larger regions, the Strait of Juan de Fuca, Washington Sound and Puget Sound.



extending from Ediz Hook to the western shore of Whidbey Island. The San Juan Islands (SJI) are

situated between the mainland and Vancouver Island, to the north of ESJF. The Strait of

Georgia (SG) is located to the east of SJI and continues up into Canadian waters. Admiralty Inlet

(AI) is the primary connecting waterway into the Puget Sound from the northern waters,

connecting with ESJF running down between the Olympic Peninsula and Whidbey Island. Hood

Canal (HC) is a long, narrow, hook-shaped inlet off the west side of AI. Whidbey Basin (WB) is

located to the East of Whidbey Island, including portions of Possession Sound, Port Susan,

Saratoga Passage and Skagit Bay. Central Puget Sound (CPS) is the main basin of the Puget

Sound, located to the south of AI and WB, extending to the Tacoma Narrows. South Puget

Sound (SPS) is the area the furthest from the Pacific Ocean, and only connects with the other

water bodies through the Tacoma Narrows where it joins up with the south end of CPS.

The basins were grouped into three geographic regions that showed similar trends in harbor

porpoise abundance over the course of the study. The Strait of Juan de Fuca (SJF) includes

WSJF and ESJF. Washington Sound (WS) includes SJI and SG. Puget Sound (PS) includes AI, HC,

WB, CPS, and SPS.

Data collection

Surveys were flown each year from early December until the survey was complete, usually by the end of January, but at times into early February (this timing was established to capture the mid-winter period when sea ducks and marine birds are least likely to be migrating). Flights were made at an altitude of 200 ft (61m) AGL at an airspeed of 85-90 kn. All surveys utilized piston de Havilland Canada DHC-2 Beavers on either strait or amphibious floats. Observations were made by two observers positioned in the center seats viewing through bubble windows on the left and right sides of the aircraft (Figure 2). To visibly delineate the transect boundary on each side of the aircraft a string was attached to the wing-strut (at 33⁰) to delineate the outer boundary of the 50m transect strip, while the lower boundary was delineated by the float (58⁰) (Figure 3 & 4). A 50m transect strip was used as it is possible to view the entire area of the strip abeam the aircraft within a single field of vision

Figure 2. Biologists Cyra (right) and Murphie (left) viewing their respective transect strips through bubble windows.



without having to focus up and down the transect strip; this was done to increase the likelihood of not missing observations within the strip. All observations were

recorded into audio

voice recorders noting

species, count,

behavior, and time

(HH:MM:SS). All

Surveys utilized a

dedicated pilot and

navigator sitting in the

front seats of the

aircraft (Figure 5). The

navigator ran data

logging software that

automatically recorded

continuous GPS

coordinates as well as

non-observational

survey events.

While marine birds

were the primary focus

of the survey, all

marine mammal

observations were

recorded beginning in

1995 as well. Prior to

1995, marine mammal

observations were recorded but there may have been times when records were not consistent

as they were not the primary subjects of the survey, thus pre-1995 surveys were omitted. All

observations of marine birds and marine mammals were classified to species and count, and

were noted if in or out of the transect strip. Viewing the transect strip was prioritized,

however, some observations would be noted outside of the transect strip, or when off effort,

when the observer thought the observation warranted note. These observations outside the

transect strip and off effort were removed from the analysis.

Figure 4. View of transect strip delineated by float and string trailing off wing-strut.

Figure 3. Diagram of left and right survey strips in relation to the transect line. An area 76 meters wide is obstructed from view directly below the aircraft due to the floats. A 50 meter transect strip is viewed from above the floats and out to 33⁰.



Surveys were only

conducted during

favorable conditions

generally established

for marine birds, these

include Beaufort sea

states ≤3, and during

the hours with

sufficient solar light

availability. During

winter months

available sunlight is

limited, with the

shortest day of the

year averaging ~8.3

hours between sunrise

and sunset and the sun only reaching 18.3⁰ above the horizon. In general, surveys were limited

between 1000 – 1400 hours each day to restrict surveys from being conducted during low-light

conditions. By limiting the survey between those hours, on most days, the angle of the sun

above the horizon remains > 15⁰. There are some days during December that the Sun angle

during surveys is as low as 12.5⁰ above the horizon, but only for short durations during the

morning hours. During the latter half of January and into early February the surveys hours may

begin before 1000 and end after 1400 as long as the sun angle above the horizon was >15⁰, and

the sun azimuth ranged between 136⁰ and 215⁰ from north. Surveys were not limited to cloud

cover or rain factors as long as VFR flight conditions were maintained.

Transects were flown parallel to the shoreline, including all islands, islets and exposed rocks.

Parallel transects were flown over submerged mudflats over the larger estuaries. In 1994-2010

saw-tooth transects were flown across inlets, bays and channels in an ad hoc manner that

attempted to obtain even coverage (Figure 6). Beginning in 2011 these saw-tooth transects

were split into two sets based on depth: <60m depth and >60m depth. Coverage in the <60m

depth strata were increased while effort in the >60m depth strata were decreased from the

pre-2011 levels (Figure 7). It is possible that this change in design might lead to some change in

observations per unit effort. In addition, the post 2010 saw-tooth transects were repeatable

between years. During some years transects were also flown over waters in British Columbia,

Canada. All transect sections within Canadian waters were removed from this analysis to keep

the dataset as consistent as possible from year to year.

Figure 5. View of the cockpit with computing devices showing navigation and event logging software used by navigator and transect navigation software used by pilot.



Figure 6. Transects flown during winter aerial surveys of marine birds and mammals from 1995 – 2010. Transects depicted are only the offshore transects used for analyses of harbor porpoise trends.



Figure 7. Transects flown during winter aerial surveys of marine birds and mammals from 2011 – 2014. Transects depicted are only the offshore transects used for analyses of harbor porpoise trends.

Data Analysis As the study was designed for marine birds, certain sections of transects were removed from

the analysis that would bias the results. These included the shoreline transects (those transects

flying alongside and parallel to the shoreline) as only one observer was viewing offshore of the

shoreline, and it would also bias survey effort to the shoreline habitats. In addition, areas

above low-low water were also removed as these areas would not be suitable habitat

throughout the tidal cycle. Transects that were in Canadian waters were also removed from

analysis.

On effort transect GPS coordinates were translated into KML files using R 3.2.0 (R core team

2014), allowing shoreline sections of transect lines to be marked using Google Earth Pro



7.1.2.2041 (https://www.google.com/earth/). Corresponding GPS coordinates and sightings

within the dataset were then marked as “shoreline”, and considered to be off-effort during

analysis. All observations and GPS coordinates were compared to the Washington State

Department of Natural Resources aquatic land ownership parcels shapefile

(https://fortress.wa.gov/dnr/adminsa/DataWeb/dmmatrix.html) retaining only the positions

and observations that occurred over the marine baselands. In addition, only those observations

that occurred within the transect strip were used.

Transect distance was calculated using the rgeos package in R to determine the distance

between each recorded on effort GPS position. Transect distance was multiplied by 0.1 to

convert the transect distance into km2. The number of animals per km2 was determined by

dividing the on transect count by the km2 of survey effort for each basin, region and for the

complete survey area. Corrections for detection were not applied to these results.

Rate of Change in Density

The rate of change (annual growth rate = AGR) in harbor porpoise density was calculated to

determine whether the increase in density could be attributed solely to local recruitment of the

remaining animals, or if immigration from other areas would be necessary to account for the

increase. The AGR in harbor porpoise density was determined overall for the inland waters, as

well as in each of the regions (SJDF, WS and PS), using the RATE function in Microsoft Excel

2013. The overall AGR was calculated from 1995 through 2014 for the combined regions of the

Strait of Juan de Fuca and Washington Sound as these had harbor porpoise present since the

initial surveys in 1995. The AGR for Puget Sound was based on the density starting in 2000, as

that is the point when harbor porpoise were observed on a consistent basis within the region.

Rates of change were calculated for all year combinations to verify that the chosen years were

not outliers.

Results

Transect Coverage

During the 20 years of surveys 123,015 km were flown on-effort, with 55,433 km along the

shore and 5,218 km flown over mudflats and other shallow areas, with 62,364 km flown on-

effort in the subtidal areas considered in this study (Table 1). Total annual effort from those

areas used in this analyses ranged from 2,886 km to 3,593 km (�̅� = 3,282 km).



Table 1. Survey effort by year from the 1995-2014 WDFW winter aerial surveys of marine birds and mammals. Transect lengths are only those offshore

transects used for analyses of harbor porpoise trends. Observers: BM = Bryan Murphie; JE = Joseph Evenson; MN = Matt Nixon; TC = Tom Cyra; WM =

Warren Michaelis; WP = Wendy Parsons.

Total Offshore Transect Length (km) by Region & Basin

Strait of Juan de

Fuca

Washington Sound

Puget Sound

Year Start Date End Date # Days Observers WSJF ESJF SG SJI AI CPS WB SPS HC Total

1995 1994-Dec-15 1995-Feb-01 19 JE, WP 242 507 542 450 129 395 354 453 238 3310

1996 1995-Dec-06 1996-Jan-25 20 BM, JE, MN, WM 330 441 446 340 164 372 284 368 204 2951

1997 1996-Dec-10 1997-Jan-29 19 BM, JE, WM 161 424 441 357 143 438 260 518 238 2980

1998 1997-Dec-17 1998-Feb-19 24 BM, JE, TC 212 375 495 363 153 489 354 437 259 3137

1999 1998-Dec-09 1999-Feb-19 21 BM, JE, TC 181 433 503 351 139 405 270 366 238 2886

2000 1999-Dec-03 2000-Jan-26 20 BM, JE, TC 277 384 541 360 141 446 280 310 212 2952

2001 2000-Dec-04 2001-Jan-25 20 BM, TC 238 473 473 352 164 472 262 335 226 2995

2002 2001-Dec-03 2002-Jan-18 20 BM, TC 207 501 564 360 168 488 285 356 228 3157

2003 2002-Dec-03 2003-Jan-28 22 BM, JE, TC 244 518 638 412 181 531 335 373 256 3488

2004 2003-Dec-15 2004-Feb-10 19 BM, TC 212 424 507 353 150 491 277 337 206 2957

2005 2004-Dec-13 2005-Feb-08 21 BM, TC 236 541 592 414 163 521 330 379 221 3398

2006 2005-Dec-15 2006-Feb-12 22 BM, TC 308 562 681 431 166 508 308 350 222 3535

2008 2007-Dec-05 2008-Feb-04 18 BM, TC 285 454 557 357 187 566 317 378 220 3321

2009 2008-Dec-02 2009-Jan-29 17 BM, TC 312 500 617 416 210 545 381 346 217 3544

2010 2009-Dec-03 2010-Jan-26 16 BM, TC 275 513 610 443 192 523 363 379 229 3527

2011 2010-Dec-06 2011-Feb-01 19 BM, TC 324 594 770 330 187 392 334 349 187 3467

2012 2011-Dec-02 2012-Feb-03 21 BM, TC 347 628 786 342 183 396 343 360 196 3582

2013 2012-Dec-10 2013-Feb-01 17 BM, TC 335 631 789 342 193 399 345 360 197 3593

2014 2013-Dec-04 2014-Jan-28 20 BM, TC 334 629 789 343 191 397 343 364 196 3586

Mean Dec-06 Feb-01 19.7 375 221 462 169 317 375 597 502 266 3282



Harbor Porpoise

Inner Marine Waters of

Washington State, and by

Region

Harbor porpoise density

increased throughout the

inner marine waters of

Washington state at a rate

of 10.4% year-1 from 1995-

2014 (Table 2). In 1995

the mean density across

the study area was 0.079

porpoise/km2 (26 porpoise

observed on transect) and

by 2014 the mean density

increased to 0.513

porpoise/km2 (184

porpoise observed on

transect) (Figure 8).

Harbor porpoise were

present in the SJF and WS

during all years, while in

the PS they were present

during the first year (observed in AI only), and then were absent until 2000; harbor porpoise

were present in PS and steadily increased beginning in 2000.

The regional annual growth rate (AGR) of harbor porpoise (1995-2014) was 8.1% and 9.8% year-

1 in the SJF and WS respectively. The AGR during in SPS from 2000 – 2014 (2000 being the first

year porpoise were regularly documented in the region) was 36.8%. During this same period

the AGR in SJF increased to 9.1% year-1 while WS remained relatively stable, dropping slightly to

-1.0% year-1(Table 2, Figure 9).

Table 2. Heat map of winter mean densities of harbor porpoise from the inner marine waters of Washington State, 1995 – 2014, by region. AGR = Annual Growth Rate. *AGR for PS was calculated from 2000-2014.



Figure 8. Winter density trends of harbor porpoise and Dall’s porpoise from the inner marine waters of Washington State, 1995-2015.



Figure 9. Winter density trends of harbor porpoise and Dall’s porpoise from the inner marine waters of Washington State, 1995-2015, by region.



By Basin

Table 3 is organized across the study area from the north and west (WSJF through SJI) to east

and south (AI through HC). With the exception being SG and SJI (the WS region), the densities

reported temporally by basin show a progressive increasing trend across the basins and an

expansion east and south. This same trend is also apparent in figures 11, 12, 13 and 14 where

harbor porpoise observations, shown in 5-year increments, show a clear increase in numbers

over time, as well as the expansion into all basins within the PS. The basins within WS did not

follow this trend, but harbor porpoise steadily increased there up through the early 2000’s,

then generally stabilized through 2014.

The AGR from WSJF (1994-2014) was 10% year-1 with densities starting at 0.17 and then

averaging 1.04 animals/km2 from 2011-2014. This basin had the highest average annual

densities across the study area. The trend in this basin has continued to increase through 2014

(Figure 10).

The AGR from ESJF (1994-2014) was 6.9% year-1. This low AGR is influenced by a moderate

density of 0.18 animals/km2 in 1995 (the first year of the study). Densities there dropped for

Table 3. Heat map of winter mean densities of harbor porpoise from the inner marine waters of Washington State, 1995 – 2014, by basin. AGR = Annual Growth Rate. *AGR calculated from 2001 – 2014; ** AGR calculated from 2011 – 2014; AGR calculate from 2008 – 2014.



the next four years (1996 – 1999) with an average of 0.06 animals/km2 during that period.

Since 1999 the densities there have steadily increased to 0.64 animals/km2 in 2014 (Table 3,

Figure 10). From 1999 – 2014 the AGR in this basin has been 20.6% year-1.

The AGR from SG and SJI (1995-2014) were 9.7% and 9.6% year-1, respectively. This high AGR is

influenced by the low densities documented in both basins during 1995. Harbor porpoise

densities in these two basins have been generally stable since the early 2000’s (Table 3, Figure

10).

No harbor porpoise were observed in CPS until 2001. Harbor porpoise were recorded in low

densities during 2001 and 2002, then were again absent between 2003 and 2005. Since 2006

harbor porpoise have been recorded each year. The AGR from this basin (2001 – 2014) was

7.5% year-1. This was influenced by a low density of 0.15 animals/km2 during 2014; the two

previous years, 2012 and 2013, had densities of 0.58 and 0.45 animals/km2, respectively.

Harbor porpoise were absent from WB until 2011 when a density of 0.06 animals/km2 was

recorded. Since that harbor porpoise have been observed each year with steadily increasing

densities. The AGR from this basin from 2011 – 2014 was 136% year-1 with a high density of

0.79 animals/km2 recorded.

Harbor porpoise were not observed in SPS until 2008 when a density of 0.08 animals/km2 was

recorded. With the exception of 2010, harbor porpoise have been observed in this basin each

year since 2008 with an AGR of 9.6% year-1 through 2014 (Table 3, Figure 10).

HC has had the lowest densities of harbor porpoise of all the basins. Harbor porpoise were not

observed there until 2011, and have been present in low densities in three of the last four years

of the study. The harbor porpoise that were observed in HC were at the north end near the

entrance where it joins with AI.



Figure 10. Winter density trends of harbor porpoise and Dall’s porpoise from the inner marine waters of Washington State, 1995-2015, by basin.



Figure 11. Winter harbor and Dall’s porpoise observation locations within the inner marine waters of Washington State, 1995-1999.




Dall’s Porpoise When the study began, Dall’s porpoise were commonly sighted in all three regions, though at

much lower densities than current harbor porpoise. Over the course of the study, Dall’s

porpoise sightings steadily decreased (Figures 10, 11, 12, 13, and 14), until they were

completely absent from the 2014 survey. The highest densities were in both ESJF, WSJF, SJI and

CPS. They were only sighted sporadically in SPS (3 years), WB (4 years), AI (1 year) and SG (3

years). No Dall’s porpoise were sighted in HC during any year.

Discussion The results of these aerial surveys, over a period of two decades, document both increasing

trends followed by stabilization of the harbor porpoise in the waters of the Strait of Juan de

Fuca and Washington Sound, and their expansion into the previously abandoned waters of the

Puget Sound and the waters of the Eastern Strait of Georgia, along with the concurrent decline

of Dall’s porpoise over the same time period.

As the surveys suggest, it is likely that harbor porpoise populations increased in the northern

inland waters through the late 1990s, then expanded into the southern waters as competition

for resources increased. The population may have approached carrying capacity in both the

Strait of Georgia and the San Juan Islands beginning in 2000 to 2002, while continuing to

increase in the Strait of Juan de Fuca through the most recent years. Given the population

leveling off in Washington Sound at around the same time as incursions into the Puget Sound, it

is possible that the move into Puget Sound was a consequence of resource limitations in the

northeastern areas.

Little is known about actual harbor porpoise maximum net productivity (RMAX), though most

models suggest an RMAX of 4%-10% based on their life parameters, with 4% the recommended

rate to use for the Washington Inland Waters Stock (Carretta et al. 2012; Lockyer 2003). The

growth rate throughout the study area was around 10%, though the late-1990s saw growth

rates that were around twice that rate, suggesting that there was immigration of animals from

outside the study area. It is possible that immigrants could have come from inland British

Columbia waters, or from the coastal region of Washington and/or British Columbia. Within

Puget Sound, the growth rate was 33.8%, which was calculated from 2000-2014, as this was the

period where they were observed every year, which is far higher than even the highest

estimates for RMAX. If there was a remnant of the original Puget Sound population subunit, they

only accounted for a small part of the reoccupation of the waters south of Admiralty Inlet, with

most of the animals coming from the Strait of Juan de Fuca, Washington Sound, Canadian or

coastal waters.

Dall’s porpoise are believed to be more abundant in the inland waters during the summer

months (Cowan 1944), so the annual winter aerial surveys may not be the best method to

assess their overall abundance. Even so, the population trend during the winter months

suggest a clear decline in abundance during this time of the year. This pattern has been



supported by anecdotal evidence provided by whale watching industry reports and sighting

reports provided to Cascadia Research and the National Marine Fisheries Service. Aerial

surveys for the U.S. Navy (Smultea et al. 2015), providing seasonal observations over several

years, should document whether this decline is occurring year round.

The increase in harbor porpoise abundance in the inland waters is likely to be the reason for the

decrease in Dall’s porpoise sightings. Since papers published prior to the 1960s suggest that

Dall’s porpoise were rarely, if ever, seen in Washington’s inner marine waters before the

decline of the harbor porpoise, Dall’s porpoise were likely filling a niche vacated by the harbor

porpoise. If this is the case, the occurrence of Dall’s porpoise would be expected to decrease as

harbor porpoise recovered within their historic range.

References

Bennett, P.M. et al., 2001. Exposure to heavy metals and infectious disease mortality in harbour porpoises from England and Wales. Environmental pollution, 112(1), pp.33–40.

Bossart, G.D., 2011. Marine mammals as sentinel species for oceans and human health. Veterinary pathology, 48(3), pp.676–690.

Calambokidis, J. et al., 1984. Chemical contaminants in marine mammals from Washington State. , Rockville, p.181 pgs. Available at: http://ccma.nos.noaa.gov/publications/document638.pdf.

Calambokidis, J. & Baird, R.W., 1994. Status of marine mammals in the Strait of Georgia, Puget Sound and Juan de Fuca Strait, and potential human impacts. Canadian Technical Report of Fisheries and Aquatic Sciences, 1948, pp.282–303.

Calambokidis, J. & Barlow, J., 1991. Chlorinated hydrocarbon concentrations and their use for describing population discreteness in harbor porpoises from Washington, Oregon and California,

Carretta, J. V et al., 2012. U.S. Pacific marine mammal stock assessments: 2011. Noaa-Tm-Nmfs-Swfsc-488, pp.1–356.

Chivers, S.J. et al., 2007. Additional genetic evidence for population structure of Phocoena phocoena off the coasts of California, Oregon, and Washington, La Jolla, California.

Chivers, S.J. et al., 2002. Small-scale population structure of eastern North Pacific harbour porpoises (Phocoena phocoena) indicated by molecular genetic analyses. Journal of Cetacean Research and Management, 4(2), pp.111–122.

Cowan, I.M., 1944. The Dall Porpoise, Phocoenoides dalli (True), of the Northern Pacific Ocean. Journal of Mammalogy, 25(3), pp.295–306.

Dexter, R. et al., 1985. Temporal trends in selected environmental parameters monitored in Puget Sound. Technical memorandum, (September). Available at: http://docs.lib.noaa.gov/noaa_documents/NOS/OMA/TM_NOS_OMA/nos_oma_19.PDF.

Ecology & King County, 2011. Control of Toxic Chemicals in Puget Sound: Assessment of selected



toxic chemicals in the Puget Sound Basin, 2007-2011,

Everitt, R.D., Fiscus, C.H. & DeLong, R.L., 1980. Northern Puget Sound Marine Mammals. A Report prepared for the MESA Puget Sound , DOC/EPA Interagency Energy/Environ. R&D Program. EPA-600/7-80-139, Washington, D. C.

Hammond, P.S. et al., 2008. Phocoena phocoena. The IUCN Red List of Threatened Species 2008: e.T17027A6734992. Available at: http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T17027A6734992.en [Accessed January 27, 2016].

Huggins, J.L. et al., 2015. Increased harbor porpoise mortality in the Pacific Northwest, USA: understanding when higher levels may be normal. Diseases of aquatic organisms, 115(2), pp.93–102. Available at: http://www.ncbi.nlm.nih.gov/pubmed/26203880.

Laake, J. et al., 1997. Abundance and distribution of marine mammals in Washington and British Columbia inside waters, 1996. In Marine Mammal Protection Act and Endangered Species Act Implementation Program 1996. Seattle, WA: AFSC Processed Report 97-10. National Marine Fisheries Searvice, pp. 67–73.

Law, R.J. et al., 1991. Concentrations of Trace Metals in the Livers of Marine Mammals (Seals , Porpoises and Dolphins) from Waters Around the British Isles. Marine Pollution Bulletin, 22(4), pp.183–191.

Law, R.J. et al., 2002. Polybrominated diphenyl ethers in two species of marine top predators from England and Wales. Chemosphere, 46(5), pp.673–81. Available at: http://www.ncbi.nlm.nih.gov/pubmed/11999790.

Lockyer, C., 2003. Harbour porpoises (Phocoena phocoena) in the North Atlantic: Biological parameters. NAMMCO Sci. Pub., 5, pp.71–89.

Miller, E.J., 1990. Photo-identification techniques applied to Dall’s porpoise (Phocoenoides dalli) in Puget Sound, Washington. Report of the International Whaling Commission Special Issue, (12), pp.429–437. Available at: https://archive.iwc.int/pages/view.php?ref=472&search=!collection34&offset=0&order_by=relevance&sort=DESC&archive=0&k=&.

Osborne, R.J., Calambokidis, J. & Dorsey, E.M., 1988. A guide to marine mammals of Greater Puget Sound, Anacortes, WA: Island Publishers.

Osmek, S. et al., 1996. Assessment of the Status of Harbor Porpoise (Phocoena phocoena) in Oregon and Washington,

Pike, G.C. & MacAskie, I.B., 1969. Marine mammals of British Columbia,

Scheffer, V.B., 1949. The Dall Porpoise, Phocoenoides dalli, in Alaska. Journal of Mammalogy, 30(2), pp.116–121.

Scheffer, V.B. & Slipp, J.W., 1948. The whales and dolphins of Washington State with the key to the cetaceans of the west coast of North America. The American Midland Naturalist, 39(2), pp.257–337.

Smultea, M. et al., 2015. Puget Sound marine mammal aerial surveys , 2013-2015. In Marine



Mammal Working Group - Puget Sound Ecosystem Monitroing Program (PSEMP). Olympia, WA.

Sveegaard, S. et al., 2012. Correlation between the seasonal distribution of harbour porpoises and their prey in the Sound, Baltic Sea. Marine Biology, 159(5), pp.1029–1037.

Washington Department of Fish and Wildlife, 2015. 2015 Puget Sound Commercial Salmon Regulations. , p.52. Available at: http://wdfw.wa.gov/fishing/commercial/salmon/.

Aerial view of harbor porpoise cow and calf near Waldron Island in the San Juan Islands, Washington. – Joseph Evenson, WDFW.

disappearance and return of harbor porpoise to puget...

Documents